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2.2 Measuring Earthquakes

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Vocabulary

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Focus: the point beneath Earth's surface where rock that is under stress breaks, which causes an earthquake to occur
Epicenter: the point on the surface directly above the focus
Seismic waves: vibrations that travel through Earth carrying energy released during an earthquake
Primary waves: earthquake waves that compress and expands the ground like an accordion ( p waves)
Secondary waves: earthquake waves that vibrate from side to side as well as up and down ( s waves)
Surface waves: these waves move slower than P waves and S waves but they produce the most severe ground movement
Seismograph: a graph that records the ground movements caused by seismic waves
Magnitude: the measurement of earthquake strength based on seismic waves and movement along faults
Mercalli scale: a device that was created to try to rate earthquakes according to their intensity
Richter scale: a rating of the size of seismic waves which is measured by a particular type of mechanical seismograph
Moment magnitude scale: a rating system that estimates the total energy released by an earthquake

Outline

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Seismic Waves

• Primary waves
• Secondary Waves
• Surface Waves

Detecting Seismic Waves

• people used a seismograph to record the waves
  • the seismograph would draw lines on a paper to see how much force the seismograph is

Measuring Earthquakes

• The Mercalli Scale
  • a creation that might not of worked
• The Richter Scale
  • people still use this rating
• The Moment Magnitude Scale
  • this scale can scale any earthquake even if it's very far away or very close

Locating the Epicenter

• p waves come first and then s waves
  • the farther away the earthquake, the farther the p wave is to the s wave

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